<aside> <img src="https://s3-us-west-2.amazonaws.com/secure.notion-static.com/9fbd46a7-60a7-4817-a9b3-35afdd1c1e80/report.png" alt="https://s3-us-west-2.amazonaws.com/secure.notion-static.com/9fbd46a7-60a7-4817-a9b3-35afdd1c1e80/report.png" width="40px" /> Degree Days are a measurement used to help quantify the need for running heating or air conditioning on any given day.
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There are two primary types of Degree Days:
Heating Degree Days (HDD) are a measure of how much (in degrees), and for how long (in days), the outside air temperature was below a certain level. They are commonly used in calculations relating to the energy consumption required to heat buildings.
Cooling Degree Days (CDD) are a measure of how much (in degrees), and for how long (in days), the outside air temperature was above a certain level. They are commonly used in calculations relating to the energy consumption required to cool buildings.
<aside> <img src="https://beestat.io/img/notion/lightbulb.svg" alt="https://beestat.io/img/notion/lightbulb.svg" width="40px" /> Beestat uses a base temperature of 65°F for Degree Days calculations. This means that when the outdoor temperature is above 65° you need to cool your home, and when it’s below 65° you need to heat your home.
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Let’s take a look at a cool day on November 8th. The average temperature was 62°F, with a low of 46°F and a high of 76°F. In many cases, this is a decently accurate predictor of whether or not you should run the heating or air conditioning. It’s not perfect, though. Average/high/low is not a complete picture and can be misleading.
We can visualize the problem by looking outdoor temperature on two separate days. They have the same high, low, and average temperatures. Do both days need the same amount of heating and air conditioning? The answer is “no”. The second day is fairly mild and cools down quickly in the afternoon. This is where Degree Days can help us do more accurate analysis.
| Day | Low | High | Average |
|---|---|---|---|
| 1 | 46°F | 76°F | 62°F |
| 2 | 46°F | 76°F | 62°F |
Let’s take a look at the same chart with some overlays to help us see what’s going on.
When the outdoor temperature is below 65°F, we generate Heating Degree Days. And when the outdoor temperature is above 65°F, generate Cooling Degree Days. These are represented on the charts with shaded areas.